Microscopic and spectroscopic investigation of U(VI) interaction with the monocellular green alga Chlorella vulgaris

The green alga Chlorella vulgaris has the ability to bind high amounts of uranium(VI) in the pH range from 3 to 6 and to a lesser extend at higher pH values. The uranium removal is almost complete at pH 4.4 and 6 by metabolic active and inactive cells under the given experimental conditions. Laser-induced fluorescence spectroscopy was used for the characterization of uranyl species formed in solutions and biomass. Fluorescence spectroscopic investigations indicate differences of the formed algal uranyl complexes in dependence of the metabolic activity of cells and the uranyl speciation. Scanning electron microscopy demonstrates that the algal cell wall is involved in the binding of U(VI).